Handwriting analysis is called "graphology." It can determine identity in legal cases, tell a person's mood at the time they wrote a passage, letter, or homework, and give glimpses into their personalities. The way the letters slant, whether they are open or closed, how the Ts are crossed, and how the i is dotted are just a few of the ways to analyze handwriting.
The word "signature" came from the Latin "signare" which means "to sign." A signer or signatory is the person who writes the signature. Signatures and regular handwriting can be different and are analyzed differently. For example, a signature can tell you if a person is arrogant or self-important. Are they sociable, introverted or extroverted? Slow and methodical or quick and careless?
I've always admired my Dad's handwriting and especially his signature. It never changed as you can see from the example below where I've put his social security card next to his most recent driver's license, documents that would have been obtained years apart.
My Grandad also had lovely handwriting, as did Grandmother. I see a lot of resemblance in Dad's and Grandad's signatures.
Dad's Signature. It is beautiful handwriting, especially for a man.
Those she didn't sign this card with a signature, it is a good
example of her handwriting, albeit she was a little shaky by this time of her life.
Interesting to note that the SS Admin typed his place of business on the stub
of his SS card. Note the date. If I am correct, that is the year the SS Act was implemented.